The present invention relates to a step-by-step electric relay structure.
As is known, a relay is a device which, upon sensing a variation occurred in a power supply or drive circuit, provides a consequent variation of one or more driven circuits, thereby allowing to use a small power drive signal to operate a driven circuit of even a much larger power.
Also known is the fact that the mentioned relays may be considered as pertaining to three main classes, that is electric, electromechanical and electronic relays (without considering thermal relays or electrodes and the like).
An electric relay is that in which the power supply circuit and the driven circuits are exclusively of an electric type: these electric relays have several advantages, among which that of omitting to use delicate active electronic components, but using only resistances, capacitors and diodes which do not consume a substantial electric power.
Moreover, an electric relay is a very noiseless one and may also operate directly by 220 Vac, and it may be moreover coupled as a conventional electromechanic three-wire step-by-step relay.
Moreover, it has “clean” contacts, that is non solid status contacts, with a very high switching capability, and being practically insensitive to shorts.
An electromechanical relay, in turn, is an electric relay consisting of an electromagnet sensitive to the supply current strength variation, and which, by operating on a soft iron movable armature, will cause one or more contacts to be either opened or closed.
Such an electromechanical relay, while having a good structural strength and being adapted to satisfactorily operate both for large and small switching currents, has, however, a large size, a high operating noise and a high switching power consume, that is a high operation power.
An electronic relay, finally, is a relay using solid status electronic components, such as silicon controlled transistors and diodes, and has a small size and operates in a flexible and noiseless mode of operation.
However, such an electronic relay is very sensitive to voltage peaks and high currents, and, since it includes a solid status end stage, it may, for example, be “burned” if the coupled load is shorted.
Notwithstanding the above mentioned drawbacks of the electronic relays, at present the relay technology seems to be oriented to a continuous development of said electronic relays, to the detriment (obviously) of electromechanical relays and even of electric relays, which seems to the Applicant not to be justified, in view of the above mentioned great advantages, and yet other advantages, of the electric relays, even compared to the electronic ones.